1. Field of the Invention
The invention relates to an information processing apparatus, an information recording medium, an information processing method, and an information processing program. More specifically, the invention relates to an information processing apparatus, an information recording medium, an information processing method, and an information processing computer program for carrying out processing using a content code file, which includes an access control program of a content, and the like, which is recorded in an information recording medium together with the content and which is used to reproduce the content.
2. Description of the Related Art
Discs, such as DVDs (Digital Versatile Discs) and Blu-ray Discs (trademark), are used as recording media for various contents, such as movies and music. Copyrights, distribution rights, and the like, of most of these contents recorded in the discs are owned by content creators or distributors, and access control is provided to prevent improper appropriation.
For example, a control program or system is used to prevent unauthorized duplication of a content recorded in a disc or place restrictions on the number of times copied. In addition, there is used an access control method in which an encrypted content is stored in a disc and then a key that can be acquired only by a user or a device with an authorized content access right is set for the content. Note that, for example, Japanese Unexamined Patent Application Publication No. 2003-116100 describes the configuration of a content access control by means of content encryption.
However, even when a content is encrypted, if a cryptographic key leaks, there is a problem that improperly decoded contents leak. International Application Publication No. WO2005/008385 describes an existing configuration that solves the above problem. WO2005/008385 describes a configuration that content data are recorded with part of the content replaced with dummy data to prevent improper reproduction of the content.
When the content replaced with dummy data is reproduced, it may be necessary to replace the dummy data with normal content data. The data conversion utilizes a content code file that contains replacement data for dummy data and a conversion program.
The content code file is recorded in an information recording medium together with the content. The content code file is recorded in the information recording medium, for example, as a file independent of the content. Thus, the content code file may be moved or copied to another information recording medium alone. Thus, it is presumable that an improper content code file is created and used.
To prevent such improper appropriation of a content code file, a digital signature of a third party organization that manages contents is set for a formal content code file. For example, a digital signature is placed on a content code file in a KIC (Key Issuance Center, key management center), and the content code file is recorded in a disc.
When a disc that contains a content and a content code file is inserted in a reproducer for reproducing, the reproducer verifies the signature set for the content code file. Only when the validity of the content code file is verified through the signature verification, it is allowed to reproduce the content using the content code file. This prevents usage of a content code file with no set formal digital signature.
However, there is a problem that the procedure for assigning a digital signature takes time and cost. For example, when it is intended to manufacture and distribute a disc that stores a new content, a content code file corresponding to the new content will be created.
The content code file includes replacement data corresponding to dummy data as described above and a player specific program. Thus, when a new content code file is created, the following processes are repeated. First, reproducing test is executed to check for occurrence of an error in various types of players, and, when an error occurs, the content code file is changed and then reproducing test is executed again.
A device that executes reproducing process with application of a content code file, that is, the above described reproducer, typically checks for validity by verifying the signature of a content code file. Thus, even in the prototyping phase, when the same reproducer as a user device is used, a file with a set formal digital signature is created. As described above, when it may be necessary to recreate a content code file again and again, it may be necessary to request the KIC to assign a signature each time a new file is created. Creating a signature multiple times wastes cost and time.
To cut the above wastes, there is an idea to create a special reproducer for test, which can omit verification of the signature of a content code file to allow reproducing process. However, it is expensive to manufacture such a special reproducer. In addition, in the event that such a special reproducer is improperly distributed, many users may use the improper reproducer, and, therefore, there is a possibility that access control by means of a content code file is invaluable. In such a case, there is a possibility that many contents are improperly reproduced and used to cause a huge loss.